Hip dysplasia is the medical term for instability, or looseness, of the hip joint that affects thousands of children each year. Hip dysplasia occurs when the ball of the hip (called the femoral head) is not properly located in the hip socket (see FIGS. 2A-2D for illustrations of a normal and subluxated and dislocated hip joints). The condition is usually diagnosed in babies and ranges from mild instability to complete dislocation. Approximately one out of every twenty full-term babies has some hip instability, and, of these, 2-3 per 1000 will require treatment. See FIG. 1 for an illustration of the anatomy of the hip.
The frequency is variable depending on gender, race, and other factors, including post-natal positioning. Statistically, girls have a higher incidence of hip dysplasia than boys.
Untreated hip dysplasia is a silent childhood condition that frequently causes disability and arthritis in adults. Hip dysplasia is a hidden condition because it does not cause pain in children, and walking is achieved at the normal age. In spite of the frequency and the potential for life-long disability, there is poor awareness outside the medical profession that this is a common condition. Early diagnosis and simple treatment is the best solution, but some cases go undetected or are difficult to treat when discovered late. Also, many children around the world do not have access to early diagnosis and treatment.
There are a variety of treatments that are used depending on the age of the child and the severity of the condition. Current treatment methods are directed towards detecting and treating persistent instability and complete hip dislocation.
When hip dislocation occurs at the time of birth, the ligaments are stretched and the socket is shallow. Usually, the joint will become normal if the hip can be held in the socket until it becomes stable. Dislocated or unstable hips in newborn infants can usually be held in place by a brace or harness until the ligaments become more stable. There are a wide variety of holding devices available, but the most common ones are the Pavlik Harness (FIGS. 3A and 3B) and various types of devices called fixed abduction braces. There are other types of harnesses and devices that are also used to treat persistent hip instability and dislocation. Most doctors recommend full-time wear for 6-12 weeks, but some doctors allow removal for bathing and diaper changes as long as the legs are spread apart to keep the hips pointed at the socket. After the hips become stable, the brace is worn part-time, usually at night, for another 4-6 weeks. Adverse consequences have also been reported when these treatment devices are used. Therefore, these treatments are reserved for cases with documented and persistent instability or dislocation.
When hip dysplasia or dislocation is diagnosed after several months of age, there are greater changes in the soft tissue and ligaments. Treatment may require closed reduction under general anesthesia and application of a body cast to hold the hip in the socket for several months. Surgery is necessary when closed reduction fails or when the diagnosis is made after walking age.
The longer the hip is out of place, the more difficult it is for the hip to return to normal and the greater the risk of problems from the condition or from necessary treatments.
Although current medical practice is to detect and treat persistent instability and dislocation, there are many children who go undiagnosed by current methods. The efficacy of current screening methods has been questioned as a preventative measure. In 2006, the United States Preventative Health Services Task Force released the conclusion that evidence is insufficient to recommend routine screening for developmental dysplasia of the hip in infants as a means to prevent adverse outcomes.
In spite of efforts at screening, early detection, and specific treatment of hip dysplasia during infancy, there are numerous subtle degrees of dysplasia that lead to adult osteoarthritis of the hip. It has been estimated that subtle forms of hip dysplasia account for 5-10% of all hip replacement surgeries performed in the United States. Mild acetabular dysplasia may be the most common cause of osteoarthritis of the hip in women. Thus it seems that our current diagnosis and treatment methods during infancy and childhood have been insufficient in the prevention of osteoarthritis and disability associated with hip dysplasia.
There is evidence that hip dysplasia is not present in the developing fetus and that the condition occurs at birth or shortly after birth. There is also evidence that infant positioning in the neonatal period with the thighs held together in extension increases the risk of subsequent hip dysplasia. Hip dislocation and dysplasia were common among Navajo Indians who carried their babies on papoose boards with the hips in extension. Hip dislocation and dysplasia were also common in Japan when babies were swaddled tightly with their legs in extension. Both cultures have dramatically reduced the frequency of hip dysplasia by changing their habits for positioning of babies during early infancy. Ethnic groups that nurse and carry their babies with the legs around the torso of the mother have a lower frequency of hip dysplasia and a lower frequency of adult hip arthritis. Thus, post-natal positioning may influence and reduce the frequency of undetected hip dysplasia. Swaddling has recently been re-introduced to the United States and other countries as a method to reduce the frequency of infant colic and fussiness.
It is believed that keeping the infant in a position more akin to that in the womb, i.e., the “frog position,” with the legs apart and slightly bent upward at the knee, can prevent immediate and later problems in hip joint development. The normal infant hip has approximately 35° of physiological hip flexion contracture at birth. Extension of the hip and adduction of the thighs together have deleterious effects on hip stability. There are no commercial devices currently available in the USA for maintenance of normal and mildly unstable hips by gentle positioning in a physiological position that encourages hip flexion.
While a number of harnesses and devices known for use in retaining the infant in a proper position for hip joint development, none is known to position the infant's hips in a slightly flexed and abducted physiological position and allow the infant to remain supine, a recommended position for reducing the incidence of sudden infant death syndrome.